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idleassetsd

That 84.3 GB in 3 hours is huge. It likely means your Mac pulled down:

How to prevent huge background downloads

Unfortunately, Apple doesn’t give a simple toggle for idleassetsd, but you can limit its impact:

  1. Turn off automatic macOS updates:

    • Go to System Settings → General → Software Update → Automatic Updates.
    • Disable “Download new updates when available” and “Install system files and security responses” if you want full control.

  2. Restrict background ML downloads (Apple Intelligence / ML models):

    • Go to System Settings → General → Siri & Spotlight.
    • Disable features like Suggestions, Siri learning, or Apple Intelligence (if available in your region).
    • This prevents some of the huge model downloads.

  3. Limit caching servers (for advanced users):

    • macOS sometimes acts like a “caching server” for iOS/macOS updates. Check in System Settings → General → Sharing → Content Caching and disable it if on.

  4. Block large background traffic temporarily:

    • You can use Little Snitch or LuLu (firewall apps) to monitor and block idleassetsd from accessing Apple servers if you want strict control.

  5. Clear already-downloaded data (optional):

    • Look in /Library/Application Support/com.apple.idleassetsd or /System/Library/Assets (read-only without disabling SIP).
    • Usually safe to leave them, but if space is critical, you can clean caches.

✅ Recommendation: Disable auto updates + caching if you don’t want this again. If it happens constantly (like every few hours), it may be a bug or corrupted asset download loop — in that case, I’d suggest a reboot + safe mode boot, or contacting Apple Support.

advanced solutions

/Library/Application Support/com.apple.idleassetsd/Customer/4KSDR240FPS

And all the files are large .mov files (hundreds of MB to almost 1 GB each).

👉 That directory name (4KSDR240FPS) indicates video assets — specifically sample video clips that macOS downloads in the background. These are the same videos used in:

So your system has been silently pulling down Apple’s 4K HDR / 240FPS demo/screen saver videos via idleassetsd. That explains why you saw 84GB of downloads in a few hours — each clip is hundreds of MB and there are many of them.

How to investigate further (Terminal commands)

You can confirm and explore more with these:

  1. Check what idleassetsd is doing in real time:

    sudo lsof -c idleassetsd

    This shows what files/sockets the process has open (e.g., active downloads).

  2. Check its log messages:

    log show --predicate 'process == "idleassetsd"' --last 1h

    Replace 1h with 6h or 1d to look back further. You’ll see exactly what assets it decided to fetch.

  3. Inspect downloaded assets with metadata:

    mdls /Library/Application\ Support/com.apple.idleassetsd/Customer/4KSDR240FPS/*.mov | grep -E "kMDItemWhereFroms|kMDItemContentType|kMDItemPixelHeight|kMDItemPixelWidth|kMDItemDurationSeconds|kMDItemFSSize"

    This will tell you where macOS thinks the file came from, resolution, and duration:

    • kMDItemWhereFroms: Displays the URL from where it was downloaded (likely Apple’s content servers).
    • kMDItemContentType: Shows file type (it should say public.movie).
    • kMDItemPixelHeight / kMDItemPixelWidth: Resolution (4K = 3840 x 2160).
    • kMDItemDurationSeconds: Duration of the video in seconds.
    • kMDItemFSSize: Size of each file.

  4. See how much total space is used:

    du -sh /Library/Application\ Support/com.apple.idleassetsd

  5. If you want to delete them:

    sudo rm -rf /Library/Application\ Support/com.apple.idleassetsd/Customer/4KSDR240FPS

    (Safe to remove; macOS may re-download them later unless blocked.)

How to stop these huge video downloads

✅ So in short: those 84 GB are Apple’s 4K HDR screensaver videos, silently fetched by idleassetsd.

Your snippet shows idleassetsd using TVIdleServices.Aerial to fetch from sylvan.apple.com/itunes-assets/Aerials… and then:

downloadableAssetCountToReachMinimum… needs 3 more asset(s) Starting batch download of 16 assets

Those are the Apple “Aerial” screen saver videos (the 4K SDR 240 fps variants). The folder name you listed earlier (…/Customer/4KSDR240FPS) and the .mov files align perfectly with that.

Useful Terminal checks

  1. See which screen saver is currently selected

    defaults -currentHost read com.apple.ScreenSaver moduleDict 2>/dev/null \
|| defaults -currentHost read com.apple.screensaver moduleDict

  2. Disable the screen saver entirely (prevents Aerial from ever triggering)

    defaults -currentHost write com.apple.ScreenSaver idleTime -int 0 2>/dev/null \
|| defaults -currentHost write com.apple.screensaver idleTime -int 0

    (You can re‑enable later via System Settings → Screen Saver, or by writing a non‑zero idleTime.)

  3. Confirm/monitor network & file activity

    # Live network I/O for the process
sudo nettop -p idleassetsd -J bytes_in,bytes_out

# Live file writes/reads by the process
sudo fs_usage -w -f filesystem idleassetsd

  4. What it has downloaded + totals

    # Total on-disk size of all customer assets
sudo du -sh "/Library/Application Support/com.apple.idleassetsd/Customer"

# Total size of only the 4K 240fps movies
find "/Library/Application Support/com.apple.idleassetsd/Customer/4KSDR240FPS" -type f -name "*.mov" -print0 \
| xargs -0 stat -f %z \
| awk '{s+=$1} END{printf "Total MOV bytes: %d (%.2f GB)\n", s, s/1024/1024/1024}'

  5. Show per‑file metadata (source URL/resolution/duration/size)

    mdls "/Library/Application Support/com.apple.idleassetsd/Customer/4KSDR240FPS/"*.mov \
| grep -E "kMDItemWhereFroms|kMDItemContentType|kMDItemPixel(Width|Height)|kMDItemDurationSeconds|kMDItemFSSize"

  6. See what the daemon is doing (last 2 hours)

log show --predicate 'process == "idleassetsd"' --last 2h

Stop it from downloading again

  1. Option A (recommended): switch off Aerial

    • System Settings → Screen Saver → choose anything but Aerial (or set “Never”).
    • Then remove the cached videos:
    sudo rm -rf "/Library/Application Support/com.apple.idleassetsd/Customer/4KSDR240FPS"

    Optionally restart the agent so it resets its state:

    sudo launchctl kickstart -k system/com.apple.idleassetsd

  2. Option B: keep a screen saver, but ensure it’s local

    • Pick a local, non‑Aerial saver (e.g., Photos with a local album).
    • Remove the 4K cache as above.

  3. Option C: firewall it (strict control)

Note: launchctl disable/bootout for Apple system daemons is generally blocked by SIP and can break other features. I don’t recommend permanently disabling idleassetsd.

Why it grabbed so much

Aerial maintains a minimum local cache per category; your logs show it actively trying to reach that minimum and queuing 16 assets in a batch. At ~300–1000 MB each, that easily explains the ~84 GB spike.

If you want, run the metadata command above — you’ll see kMDItemWhereFroms pointing at those Aerials… URLs and 3840×2160 (4K) dimensions with long durations, confirming they’re just screen saver videos.